JP2002292334A - Method for forming coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a coating film which can eminently curtail a working time by using both a photo-curing and an urethane curing method, and obtain a double layer coating film excellent in hardness, adhesion and finishing. SOLUTION: A base coating containing a rein having active hydrogen groups and a colored pigment as main components is applied, and then a photo-curable clear composition comprising a resin (A) having polymerizable unsaturated groups and active hydrogen groups, a photo-polymerization initiator (B) having an absorption spectrum in a wavelength range of 300 nm or above, and a polyisocyanate compound (C) is applied on the base coating film. Both coating films are cured by being irradiated with light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a multi-layer coating film, and more particularly to a method for forming a coating film using a photocurable clear composition which combines photocuring and isocyanate curing.

[0002]

2. Description of the Related Art Conventionally, automobiles, industrial machines,
Acrylic lacquer, acrylic urethane paint and amino acrylic resin paint are used for painting and repairing buildings, structures and furniture (including steel). From the viewpoint, acrylic lacquer and acrylic urethane paint are mainly used. In this field, in recent years, a paint finish method of applying a clear paint over a colored base paint has become mainstream, and as the clear paint, a urethane-cured paint utilizing a reaction between a hydroxyl group and an isocyanate group has been used. I have. Examples of such clear paints are disclosed in
JP-A-00-303016, JP-A-2001-2979
In the publications and the like, specific monomers are used as one of the constituent monomer components.
A composition using a hydroxyl group-containing copolymer as a part and a polyisocyanate is disclosed. According to the paint, it is possible to form a paint film having excellent adhesion and abrasion properties with the base paint film, and has good non-uniformity resistance to return when applied to a colored base paint film such as a metallic base paint. Although a finished coating film can be formed, it is cured at
Development of a coating material that requires a drying time of from one minute to one hour and cures in a short time has been desired.

[0003] On the other hand, in recent years, compositions utilizing photocuring having rapid curability have been proposed. (JP-A-9-1003
06, JP-A-2000-344856, etc.).
According to this composition, curing proceeds rapidly, and a coating film having excellent hardness and adhesion can be formed. However, there is a problem that the adhesion is insufficient depending on the surface to be coated.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors applied a specific colored base paint, and then used both photocuring and isocyanate curing on the base coating film. Apply a light-curable clear composition,
By irradiating light, the drying time can be omitted, and a coating film having good adhesion such as hardness between the colored base coating film / clear coating film and between the colored base coating film / substrate and the base material can be obtained. Heading that it can be formed, the present invention has been reached. That is, the present invention provides: A resin containing an active hydrogen group and a base paint mainly containing a color pigment are applied, and then (A) a resin containing a polymerizable unsaturated group and an active hydrogen group on the base coating film;
(B) applying a photocurable clear composition comprising a photopolymerization initiator having an absorption spectrum in a wavelength region of 300 nm or more and (C) a polyisocyanate compound, and irradiating light to cure both coating films. 1. Characteristic coating film forming method; (A) a resin containing a polymerizable unsaturated group and an active hydrogen group, (B) a photopolymerization initiator having an absorption spectrum in a wavelength region of 300 nm or more, and (C) a polyisocyanate compound. The present invention relates to a photocurable clear composition used in a coating film forming method.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The base paint (I) used in the method of the present invention contains a resin having an active hydrogen group and a coloring pigment as main components, and contains a curing agent component such as a polyisocyanate compound. It is not necessary. This is because when a photocurable clear composition (II) described below is applied on a coating film of the base paint (I), the photocurable clear composition (II)
The isocyanate component contained in the base coat penetrates into the base coat, and the curing proceeds with the active hydrogen groups and the isocyanate groups in the base coat, so that the base coat is hardened and the adhesion between the base and the clear is improved. To do that.

Examples of the active hydrogen group contained in the base paint include a hydroxyl group, a hydroxyphenyl group, an amino group and the like. In the present invention, a resin having a hydroxyl group is preferable because of its good curability and little coloring. For example, a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, a hydroxyl group-containing polyurethane resin, a hydroxyl group-containing polyether resin and the like can be mentioned.

Further, a cellulose derivative such as cellulose acetate butyrate (CAB) or nitrocellulose may be used in combination with the resin having a hydroxyl group. Further, as the resin having a hydroxyl group, a cellulose derivative such as the CAB may be used. A modified graft copolymer of a derivative and a polymerizable unsaturated monomer mixture containing a hydroxyl group-containing polymerizable unsaturated monomer may be used.

The hydroxyl value of the resin having a hydroxyl group is as follows:
A range from 0.5 to 150 mg KOH / g is preferred.
If it is less than 0.5 mgKOH / g, the adhesion and the hardness are reduced,
On the other hand, if it exceeds 150 mgKOH / g, it is not preferable because water resistance may decrease.

In the method of the present invention, the base paint (I)
A modified graft copolymer of a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, and a polymerizable unsaturated monomer mixture containing a cellulose acetate butyrate and a hydroxyl group-containing polymerizable unsaturated monomer as a coating-forming component. The composition described in JP-A-10-354406 can be particularly preferably used.

The mixing ratio of the hydroxyl group-containing acrylic resin, the hydroxyl group-containing polyester resin, and the modified graft copolymer is such that the hydroxyl group-containing acrylic resin in the total solid content is 5%.
~ 90% by weight, 5-40% of hydroxyl group-containing polyester resin
% By weight, and preferably 5 to 75% by weight of the modified graft copolymer.

As the above-mentioned hydroxyl group-containing acrylic resin, those having a glass transition temperature of 0 to 80 ° C. and those having a glass transition temperature of −70 to 0 ° C. can be particularly preferably used.

The above-mentioned colored base coating material (I) may further comprise, if necessary, acid phosphoroxyethyl (meth) acrylate described in JP-A No. 12-178500.
Phosphoric acid group-containing polymerizable unsaturated monomers such as acid phosphoxypropyl (meth) acrylate, and hydroxyl group-containing polymerizable unsaturated monomers such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate A phosphate group-containing acrylic resin obtained by copolymerizing a saturated monomer and other copolymerizable polymerizable unsaturated monomers by a known method such as solution polymerization is used to improve the adhesion and particularly improve the metallic base. It may be blended from the viewpoint of preventing metal unevenness in the case of metal.

Examples of the coloring pigment used in the coloring base paint (I) include luster pigments such as aluminum paste, pearl powder, graphite and MIO, titanium white, phthalocyanine blue, carbon black and the like. And an extender may be added as necessary. The coloring base paint (I) may further contain paint additives such as an ultraviolet absorber, a light stabilizer, an antioxidant, a surface conditioner, a pigment dispersant, and a curing catalyst, if necessary.

The photocurable clear composition (II) used in the method of the present invention comprises a resin (A) containing a polymerizable unsaturated group and an active hydrogen group, and a photopolymerization having an absorption spectrum in a wavelength range of 300 nm or more. It comprises an initiator (B) and a polyisocyanate compound (C).

As the resin (A) containing a polymerizable unsaturated group and an active hydrogen group, at least one polymerizable unsaturated group per molecule, preferably about 2 to 50, and one molecule of an active hydrogen group per molecule. Those containing an average of about 2 to about 100, preferably about 2 to about 50, are preferred. The polymerizable unsaturated group is not particularly limited as long as it causes a radical polymerization reaction by light having a wavelength of 300 nm, and specific examples thereof include a (meth) acryloyl group, a vinyl group, and a vinyl ether.
Examples include a ter group and an allyl group. Among these, a (meth) acryloyl group is particularly preferable. Examples of the active hydrogen group include a hydroxyl group, a hydroxyphenyl group, an amino group and the like. Among these, a hydroxyl group is preferred.

In the present invention, "(meth) acryloyl group"
Represents an “acryloyl group or a methacryloyl group”.

The resin (A) is not particularly restricted but includes, for example, acrylic resins, polyester resins, polyurethane resins,
Various resins such as a polyether-based resin can be used. Specifically, for example, an acrylic resin or a polyester resin having a hydroxyl group and a carboxyl group and glycidyl (meth)
(Meth) acrylic acid was added to a resin to which acrylate was added, a resin to which maleic anhydride or itaconic anhydride was added to a vinyl resin or a polyester resin having a hydroxyl group, and an acrylic resin having a hydroxyl group and an epoxy group. Resin, a resin obtained by condensing (meth) acrylic acid on a polyester resin having a hydroxyl group, an unsaturated polyester resin, a resin obtained by adding 2-hydroxyethyl (meth) acrylate to a urethane resin having an isocyanate group, 2-hydroxyethyl (meth) for acrylic resin having hydroxyl group
Resins to which an equimolar addition reaction product of acrylate or the like and a diisocyanate compound can be used.

The resin (A) has a hydroxyl value of 10 to 200.
mgKOH / g is preferred. If it is less than 10 mgKOH / g, the hardness and weather resistance decrease, while 200 mgKOH / g
If it exceeds g, the usable time becomes short, which is not preferable.

In the present invention, the resin (A) may be used in combination with a polymerizable unsaturated compound as a reactive diluent in order to increase the solid content of the coating while maintaining curability. The polymerizable unsaturated compound is a monomer or an oligomer having an ethylenically unsaturated group, such as ethyl (meth) acrylate, butyl (meth) acrylate, or 2- (meth) acrylate.
Ethylhexyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, adamantyl (meth) acrylate, hydroxyethyl (meth) acrylate, trimethylolpropanetri (meth) acrylate Tetramethylolmethanetetra (meth) acrylate, dipentaerythritol (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, neopentylglycol di (meth) acrylate, 2,2 1 such as -bis (4- (3-methacryloxy-2-hydroxypropoxy) -phenyl) propane, di (methacryloxyethyl) trimethylhexamethylene diurethane, and 2,2-bis (4-methacryloxypolyethoxyphenyl) propane; (Meth) a of monovalent or polyvalent alcohol 4- (meth) acryloyl such as 4- (meth) acryloyloxymethoxycarbonylphthalic acid and 4- (meth) acryloyloxyethoxycarbonylphthalic acid; lylic acid ester; ethylene glycol dimaleate, propylene glycol diitanate, etc. Oxyl group-containing aromatic polycarboxylic acids and anhydrides thereof; aromatic vinyl compounds such as styrene, α-methylstyrene, chlorostyrene, vinyltoluene, t-butylstyrene, and divinylbenzene; diallylphthalate
, Diallyl isophthalate, triallyl phthalate;
Epoxy acrylate, ethylene oxide-modified epoxy acrylate polyester acrylate, polydimethyl silicon di (meth) acrylate, urethane acrylate and the like can be used, and these can be used alone or in combination of two or more.

The use ratio of the resin (A) to the polymerizable unsaturated compound is usually 90/10 to 10/90, preferably 80/20 to 20/80 by weight.

The photopolymerization initiator (B) used in the method of the present invention is not particularly limited as long as it is capable of generating radicals by being excited by light energy in a region of 300 nm or more to generate radicals and initiate radical polymerization. 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 4-t-butyl-trichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-
1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropane-1 -One, 4- (2-hydroxyphenoxy) -phenyl (2-hydroxy-2
-Propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio)
Acetophenone compounds such as phenyl] -2-morpholinopropanone-1; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone;
Thioxanthone compounds such as 2,4-dichlorothioxanthone; benzyl compounds such as benzyl, benzyldimethylketal, benzyl-β-methoxyethylacetal, 1-hydroxycyclohexylphenylketone; benzophenone, methyl o-benzoylbenzoate, Michler's ketone, Benzophenone compounds such as 4,4'-bisdiethylaminobenzophenone and 4,4'-dichlorobenzophenone; benzoin ether compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether and benzoin isobutyl ether; camphor
Quinone, anthraquinone, 3-ketocoumarin, α-naphthyl, 2,4,6-trimethylbenzoyl, diphenylphosphine oxide, acylphosphine oxide, 2,
4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl)-
Examples include phenylphosphine oxide, 10-butyl-2-chloroacridone, and fluorenone. In addition to these, known initiator systems include cationic dyes
Systems of ionic dyes and counter-ion compounds such as tonionic compounds (for example, JP-A-1-60606, JP-A-2-11
607), a system of a metal arene compound and an organic dye (for example, JP-A-4-363308, JP-A-5-17)
No. 525). Further, cyanine dyes, phthalocyanine dyes, pyrylium dyes, thiopyrylium dyes, azulenium dyes, squarylium dyes, metal complex salt dyes such as Ni and Cr, naphthoquinone / anthraquinone dyes, indophenol dyes,
Complexes of cationic dyes such as indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, aminium / diimmonium dyes, and nitroso compounds can be used. Specifically, JP-A-62-143044, Near-infrared light-absorbing cationic dyes disclosed in Japanese Unexamined Patent Publication Nos. Hei 2-1-1607, Hei 3-111402, Hei 5-194609 and Hei 4-77503.
And a triazine compound having a cyanine dye and a halogenated methyl group or a cyanine compound and a metal alloy disclosed in JP-A-2-189548.
Compounds, squarylium dyes and metal arene compounds disclosed in JP-A-5-17525,
And cationic cations and borates disclosed in US Pat.

The amount of the photopolymerization initiator (B) is about 0.01 to 10% by weight based on the total solid content of the resin (A) and the polymerizable unsaturated compound.

The photopolymerization initiator (B) is preferably used in combination with an oxygen removing agent capable of absorbing oxygen in a free radical chain process or an active hydrogen donor chain transfer agent. Examples of the oxygen removing agent include phosphine, phosphite, phosphonate, stannous salt, and other compounds that are easily oxidized by oxygen. Examples of the chain transfer agent include triethylamine, N-methyldiphenylamine, Tertiary amines such as isoamyl 4-dimethylaminobenzoate, triethanolamine and dimethylethanolamine, dimethylaminoethyl methacrylate; N-phenylglycine, 2-mercaptobenzoxazole, 2-
Mercaptobenzothiazole; 2,6-diisopropyl-N, N-dialkylaniline, N, N, 2,4,6-
N, N-dialkylaniline such as pentamethylaniline and the like can be mentioned.

A boron sensitizer may be used in combination with the photopolymerization initiator (B). Examples of the boron sensitizer include tetra-n-butylammonium, n-butyltriphenylboron, tetramethylammonium n-butyltriphenylboron, tetra-n-butylphosphonium n
-Butyltriphenylboron and the like.

The photopolymerization initiator (B) may be used in combination with an organic peroxide. Examples of the organic peroxide include benzoyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide and the like.

In the polyisocyanate compound (C) used in the method of the present invention, an isocyanate group in the compound (C) may be an active hydrogen group contained in a base coating film or an active hydrogen group of the resin (A). And is blended in order to simultaneously cure both coating films. Polyisocyanate
As compound (C), for example, lysine diisocyanate
Aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexane diisocyanate; hydrogenated xylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4 (or Cyclic aliphatic diisocyanates such as 2,6) -diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate) and 1,3- (isocyanatomethyl) cyclohexane; tolylene diisocyanate; Xylylene diisocyanate, diphenylmethane diisosoane
Aromatic diisocyanates such as polyisocyanate; Aromatic diisocyanates such as tri- or higher polyisocyanate such as lysine triisocyanate; Tri- or higher polyisocyanate such as lysine triisocyanate Organic polyisocyanate itself, or an adduct of each of these organic polyisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or the cyclization weight of each organic diisocyanate as described above Coalescence (for example, isocyanurate) and biuret type adduct. These can be used alone or in combination of two or more.

The photocurable clear composition in the method of the present invention can be cured at room temperature or at a temperature of about 100 ° C. or less. However, in the case of baking conditions exceeding 100 ° C., instead of the polyisocyanate, the photocurable clear composition is blocked. A polyisocyanate compound may be used or used in combination.

The compounding amount of the polyisocyanate (C) is such that the amount of the isocyanate group is 0.1 to 2 to the total equivalent of the active hydrogen groups contained in the resin (A) and the base coating material (I).
Used in a proportion of 0 equivalents. Isocyanate group is 0.1
If it is less than the equivalent, the curability and the adhesion between the clear / base and between the base and the substrate are insufficient, and if it exceeds 2.0 equivalent, the drying property of the surface is undesirably reduced.

The photocurable clear composition (II) used in the method of the present invention may optionally contain a cellulose derivative, a non-reactive diluent, a thermoplastic resin and the like.
Cellulose derivatives include cellulose acetate butyrate (CAB), nitrocellulose, and the like. In addition, cellulose derivatives such as CAB and a hydroxyl group-containing polymerizable unsaturated monomer or other polymerizable unsaturated monomers can be used. A graft copolymer with a monomer mixture such as a monomer may be used. Examples of the non-reactive diluent include an organic solvent, and examples of the thermoplastic resin include polyethylene, polystyrene, polymethyl methacrylate, polyvinyl acetate, polyvinyl chloride, and polycaprolactone.

The photocurable clear composition (II) includes:
Further, if necessary, an antiblocking agent, an organic solvent, an ultraviolet stabilizer, a coating surface adjusting agent, an antioxidant, a flow adjusting agent, a curing catalyst and the like can be appropriately contained.

In the method of the present invention, the base paint (I) is applied to the surface to be coated, the photocurable clear (II) is applied on an uncured base coating film, and both coating films are irradiated with light. It is cured at the same time.

Examples of the surface to be coated include a metal surface such as iron, zinc, and aluminum, a chemically treated surface thereof, plastic, wood, and the like, and an old coating surface coated thereon. For example, an automobile body that has been subjected to electrodeposition coating or intermediate coating, or a repair-painted surface of the automobile body may be used.

The coating of the base coating material (I) and the photocurable clear composition (I) can be performed, for example, by spraying, roll coater, gravure coater, screen, etc. Can be done in a way. The film thickness is 3-50 microns for the base coating film and 10-20 for the clear coating film after drying.
It can be carried out by painting to a thickness of 0 micron and then irradiating with light to cure.

The light source used for light irradiation is 300
It can be used without particular limitation as long as it emits a wavelength of nm or more, and examples thereof include a halogen lamp, a xenon lamp, a krypton lamp, a metal halide lamp, a fluorescent lamp, sunlight, a semiconductor laser, and a light emitting diode. Irradiation conditions can be appropriately selected according to the thickness and composition of the base layer and the clear layer.

[0035]

According to the method of the present invention, it is possible to form a multi-layer coating film which is fast-curing, has good adhesion between the clear / base and between the base and the substrate, and has a high finish. Although the method of the present invention can be used for automobile repair, railway vehicles, industrial equipment, and woodwork, the effects of the present invention can be maximized in the field of automobile repair because the workability is good and the curing time can be reduced even at low temperatures. Can be demonstrated.

[0036]

The present invention will now be described more specifically with reference to examples and comparative examples. Hereinafter, “parts” and “%” are based on weight unless otherwise specified.

Preparation of Colored Base Coating Preparation Example 1 27.8 parts of a modified vinyl copolymer solution (Note 1) and a polyester resin solution (Note 2) obtained by the following method 13.
3 parts, 15.4 parts of an acrylic resin solution (a) (Note 3), and 1.0 part of a phosphoric acid group-containing acrylic resin solution (Note 5) were blended, and after stirring, "Aluminum Paste K-9800" was further added.
(Note 7) 8.1 parts, xylene 17.4 parts, butyl acetate 1
7.0 parts were added in the composition shown in the same table, and about 20 parts were dispersed.
After stirring for a minute, a metallic base paint was prepared.

Production Example 2 A metallic base coating having no active hydrogen group was prepared in the same manner as in Production Example 1 except that the composition was changed as shown in Table 1 below.

[0039]

[Table 1]

Note 1) Modified vinyl copolymer solution: The following components were charged into a reactor equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and heated under a nitrogen gas atmosphere to about 1%.
The temperature was raised to 100 ° C. over time. 120 parts of toluene 80 parts of butyl cellosolve acetate 80 parts 200 parts of "CAB-381-0.5" (manufactured by Eastman Kodak Co., Ltd., cellulose acetate butyrate) The temperature reached 100 ° C., and the cellulose acetate butyrate was completely dissolved. After confirming this, the following mixture of a vinyl monomer mixture and a polymerization initiator was added dropwise to the above cellulose acetate butyrate solution over 3 hours. 2-hydroxyethyl methacrylate 3 parts Methyl methacrylate 97 parts Benzoyl peroxide 2 parts 30 minutes after the completion of dropping, azobisisobutyronitrile was added to 0.1 part.
Five parts were added, and the mixture was further kept at 100 ° C. for 2 hours under a nitrogen atmosphere, and then xylene was added to obtain a colorless and transparent modified vinyl copolymer solution having a nonvolatile content of 50%.

Note 2) Polyester resin solution: heating device,
The following components were charged into a reactor equipped with a reflux condenser equipped with a thermometer, a stirrer, a rectification tower and a water separator, and heated, and the temperature was raised from 160 ° C to 230 ° C over 3 hours. Hexahydrophthalic anhydride 26.7 parts Adipic acid 28 parts Neopentyl glycol 5.3 parts 1,6-hexanediol 40 parts This was kept at 230 ° C. for 1 hour, and the condensed water (7.4
Part) was distilled off using a rectification column. Then add xylene to 5
Xylene and condensed water were refluxed, and water was removed using a water separator. Two hours after the addition of xylene, the measurement of the acid value was started. When the acid value became 2 or less, the mixture was cooled to 120 ° C., and the mixed solvent of xylene / butyl acetate = 1/1 was used so that the nonvolatile content became 70%. After dilution, a polyester resin solution was obtained. The resin solution has a Gardner viscosity of T, a resin weight average molecular weight of 20,000, a hydroxyl value of 55, a glass transition temperature of -60 ° C, and a DBR (dibasic acid ratio) of 0.9.
It was 5.

Note 3) Acrylic resin solution (a): thermometer,
In a reactor equipped with a stirrer, a reflux condenser and a dropping pump, 25 parts of toluene and 43 parts of xylene were charged, and the temperature was raised to 110 ° C. while stirring, and a mixed solution of the following monomer mixture and polymerization initiator was added to 110 parts of The solution was added dropwise at a constant rate over about 3 hours at a temperature of ° C. Styrene 10 parts Methyl methacrylate 20 parts n-butyl acrylate 50 parts 2-hydroxyethyl methacrylate 19 parts Acrylic acid 1 part t-butyl peroxyethyl hexanate 1.2 parts After completion of the dropwise addition, the mixture was kept at 110 ° C for 1 hour and stirred. Continued. Thereafter, a solution obtained by dissolving 0.5 part of azobisdimethylvaleronitrile in 10 parts of xylene as an additional catalyst was dropped at a constant rate over 1 hour. And 1 hour 1 after dropping
The temperature was kept at 10 ° C. to complete the reaction. The resulting acrylic resin solution was a uniform and transparent solution having a nonvolatile content of 50.2% and a Gardner viscosity Z2. The copolymer had a weight average molecular weight of 50,000 and a hydroxyl value of 82 mg KOH / g. The glass transition temperature was 60 ° C.

Note 4) Acrylic resin solution (b): Acrylic resin solution (a) was prepared in the same manner as in the preparation of acrylic resin solution (a) except that a mixture of the following composition was used as a mixture of the monomer mixture and the polymerization initiator. An acrylic resin solution (b) having 50.0%, a Gardner viscosity Z1, a weight average molecular weight of 50,000, a hydroxyl value of 0, and a glass transition temperature of 60 ° C. was obtained. Styrene 10 parts Methyl methacrylate 20 parts n-butyl acrylate 50 parts i-butyl methacrylate 19 parts Acrylic acid 1 part t-butyl peroxyethyl hexanate 1.2 parts.

Note 5) Phosphate group-containing acrylic resin solution: The same procedure was carried out except that a mixture of the following composition was used as the mixture of the monomer mixture and the polymerization initiator in the production of the above acrylic resin solution. 0.1%, Gardner
Viscosity V, weight average molecular weight 30,000, hydroxyl value 140m
A resin solution having a gKOH / g and a glass transition temperature of −7 ° C. was obtained. Styrene 20 parts n-butyl acrylate 10 parts lauryl methacrylate 10 parts 2-hydroxyethyl methacrylate 10 parts 2-hydroxyethyl acrylate 10 parts acid phosphoxyethyl methacrylate 30 parts t-butyl peroxyethyl hexanate 1.2 Note 6) “CAB-381-0.5” 30% solution: “CA
B-381-0.5 "(manufactured by Eastman Kodak Co., Ltd., trade name, cellulose acetate butyrate containing no active hydrogen group) xylene / butyl acetate = adjusted to a 30% solids solution with a mixed solvent of 50/50. I got it. Note 7) "Aluminum paste K9800": trade name, manufactured by Asahi Kasei Metals Corporation, aluminum paste.

Contains a polymerizable unsaturated group and an active hydrogen group
Resin Production Production Example 3 A reactor was equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a dropping pump, a dry air blowing pipe, and charged with 50 parts of xylene. A mixture 10 of the monomer and the polymerization initiator shown in 1
While maintaining 2.3 parts at 115 ° C., the solution was dropped at a constant rate over 3 hours using a dropping pump. After the completion of the dropwise addition, the mixture was kept at 110 ° C. for 1.5 hours, and then a solution prepared by dissolving 0.5 part of an additional polymerization initiator in 10 parts of xylene was added dropwise at a constant rate over 1.5 hours. And the stirring was continued to complete the polymerization reaction. Then, xylene 25
The mixture was cooled to 80 ° C. while adding and diluting. continue,
While supplying dry air to the liquid phase, 0.06 parts of hydroquinone monomethyl ether as a polymerization inhibitor, 0.06 parts of dibutyltin dilaurate as a urethanization catalyst, 18.2 parts of an equimolar adduct of isophorone diisocyanate and hydroxyethyl acrylate, xylene 14 parts were added and the addition reaction was carried out at 80 ° C. for 7 hours to obtain a clear resin solution (A1). The obtained resin solution (A1) had a nonvolatile content of 55%, a Gardner viscosity of Z6, and a weight average molecular weight of 17,
000, and the hydroxyl value was 30 mgKOH / g.

Production Examples 4 and 5 Clear resin solutions (A2) and (A3) were obtained in the same manner as in Production Example 3, except that the composition was as shown in Table 2.

[0047]

[Table 2]

Preparation of Clear Coating Production Example 6 The clear resin solution (A1) 16 obtained above was placed in a container.
3 parts, "CN983" (Note 8) 10 parts, "Irg-184"
(Note 10) 4 parts and 0.05 parts of dibutyltin dilaurate were blended and stirred with a disper.
1EK "(Note 11) was added and stirred to obtain a clear coating.

Production Examples 7 to 10 Each clear coating was obtained in the same manner as in Production Example 6 except that the composition was changed to that shown in Table 3 below. Note in the table is as follows.

[0050]

[Table 3]

(Note 8) “CN983”: manufactured by Sartomer Co., Ltd.
Trade name, urethane acrylate (Note 9) "IBXA": manufactured by Osaka Organic Chemical Industry Co., Ltd.
Isobornyl acrylate (Note 10) "Irg-184": trade name, manufactured by Ciba Specialty Chemicals, 1 hydroxy-cyclohexyl-phenyl ketone (Note 11) "TPA-90EK": trade name, hexamethylene manufactured by Asahi Kasei Corporation Diisocyanate polyisocyanate.

Coating Examples 1-3 and Comparative Examples 1-3 To each of the colored base paints obtained in Production Examples 1 and 2, toluene / xylene / ethyl acetate / butyl acetate = 50/2.
The mixture was diluted with a thinner having a composition of 0/10/20 for 11 to 12 seconds (for ford cup # 4/25 ° C.) and adjusted to a viscous state. The paint was diluted with a thinner having the above composition for 13 to 14 seconds (for ford cup # 4/25 ° C.), adjusted to a viscosity, and provided for coating. Commercially available lacquer-primer on a tin plate
The surface was coated with 40 μm, dried at room temperature for 30 minutes, and polished with # 400 water-resistant abrasive paper. A base paint and a clear paint were sequentially applied thereon in a combination shown in Table 4 below. 15 μm in dry film thickness of colored base paint after viscous
m, and after the base coating film was touch-dried, each of the clear coating materials after the viscosity adjustment was spray-coated so as to have a dry film thickness of 40 μm. Thereafter, each coated plate was irradiated with a halogen lamp “PAR36MF” (trade name, manufactured by Iwasaki Electric Co., Ltd.) as a light source under the conditions of 110 V, 500 W and an irradiation distance of 50 cm for 10 minutes, and subjected to the following performance tests. Table 4 shows the results.

[0053]

[Table 4]

(* 1) Curability: The tackiness of the surface of the coated plate immediately after the irradiation of the lamp was examined with a finger and evaluated according to the following criteria. ：: good without stickiness on the surface, Δ: slightly sticky on the surface, x: considerable stickiness on the surface. (* 2) Pencil hardness: 2 at 20 ° C after irradiation of the coated plate with a lamp
After standing for 4 hours, the pencil hardness of the surface of the coated plate was measured according to JIS K-5.
400 8.4.2 (1990).
The evaluation was performed with tears. (* 3) Finishing property: The finishing property of the surface of the coated plate obtained by being left as it was in the same manner as in (* 2) was visually evaluated based on the following criteria. ◎: very good, ：: good, Δ: slightly distorted on painted surface, ×: considerably distorted on painted surface. (* 4) Adhesion: Cut the coating film of the coated plate obtained by standing as above (* 2) with a knife until it reaches the substrate, make 100 gobangs at 2 mm intervals, and put on it Evaluation was made based on the following criteria from the number of gobangs remaining on the coated surface when the cellophane tape was stuck and peeled off sharply. ：: The number of gobangs remaining on the painted surface is 100, Δ: The number of gobangs remaining on the painted surface is 99 to 50 ×: The number of gobangs remaining on the painted surface is 49 or less.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 7/12 C09D 7/12 175/04 175/04 201/02 201/02 (72) Inventor Nagasao Tsutomu 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa F Kansai Paint Co., Ltd. F term (reference) 4D075 AE03 BB42Z BB46Z CA02 CA13 CA47 CB06 DA06 DA27 DB02 DB05 DB07 DB21 DB31 DC01 DC05 DC12 DC13 DC38 EA07 EA43 EB07 EB19 EB19 EB20 EB22 EB35 EB38 EC11 EC37 4J038 CG001 DD001 DF001 DG001 DG111 DG131 DG141 DG191 DG261 GA01 GA02 GA03 GA09 KA03 NA01 NA23 PA17 PB05 PB06 PB07 PB12

Claims (2)

[Claims] 1. A resin containing an active hydrogen group and a base paint containing a color pigment as a main component, and then (A) a resin containing a polymerizable unsaturated group and an active hydrogen group on the base coating film. Applying a photocurable clear composition comprising (B) a photopolymerization initiator having an absorption spectrum in a wavelength region of 300 nm or more and (C) a polyisocyanate compound, and irradiating light to cure both coating films. A coating film forming method characterized by the above-mentioned. 2. It comprises (A) a resin containing a polymerizable unsaturated group and an active hydrogen group, (B) a photopolymerization initiator having an absorption spectrum in a wavelength region of 300 nm or more, and (C) a polyisocyanate compound. A photocurable clear composition used in the method for forming a coating film according to claim 1.